Effects of in-season block training periodization on training and match loads in elite young soccer players

This study investigated the effects of in-season block periodization on internal and external load responses during training and match play in elite youth soccer players. Fifteen male players (age: 17.6 ± 0.95 years) from the academy of a professional club competing in the 2021–2022 Turkish U-19 Elite Academy League were monitored over an 18-week competitive period. The training program was organized into a three-phase model using 3-week blocks within a 6-week cycle. Performance was assessed using the Yo-Yo Intermittent Recovery Test Level 1, 10, 20, 30, and 40-m sprint tests, the Arrowhead agility test, and a repeated sprint test. Internal and external load data were collected with 10 Hz GPS units and heart rate monitoring across 54 training sessions and 16 official matches. Significant improvements were observed over time in 10, 20, 30, and 40-m sprint performance and Yo-Yo IR1 performance, while agility and repeated sprint performance showed time-dependent variation across the season. Official matches were generally more demanding than training sessions across most monitored variables, including total load, maximum heart rate, maximum speed, moderate-intensity running, sprint activity, acceleration, and deceleration. These findings suggest that in-season block periodization can support physical development in elite youth soccer players, although match play remains the highest-demand context for load exposure.